Method and apparatus for beneficiating minerals



March 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICIATING MINERALS March 26, 1968 F. J.cLAwsoN ETAL. 3,374,885

METHOD AND APPARATUS FOR BENEFICIATING MINERALS Filed Oct. 15. 1963 '7Sheets-Sheet 2 March 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICITING MINEALS y INV ENT ORS Floyd J@lawson & /I//z'caeZ .6. de ief'ww @/fmf March 26, 1968 F. .1. cLAwsoNETAL 3,374,885v

METHOD AND APPARATUS FOR BENEFICITING MINERALS 7 Sheets-Sheet 4 FiledOct. l5, 1963 Ill INVENTORS Maich 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICATING MINERALS 7 Sheets-Sheet 5,

Filed Oct. l5. 1963 March 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICIATING MINERALS Filed Oct. 15, 1963 7Sheets--Sheefl 6 I v .w

I INVENTOR@ ATT RNEYS March 26, 1968 F. J. cLAwsoN ETAL 3,374,885

METHOD AND APPARATUS FOR BENEFICIATING MINERALS Filed Oct. 15, 1965 7Sheets-Sheet 7 (mi m INVENToRa im' N Fzoydfcmwm {W elMjc/maadfefwATTORNEYS United States Patent O 3,374,885 METHOD AND APPARATUS FORBENEFICIATING MINERALS Floyd J. Clawson and Michael C. De Stefano,Lakeland, Fla.; said Clawson assignor to Unifab, Inc., Camden, Tenn., acorporation of Tennessee Filed Oct. 15, 1963, Ser. No. 316,372 11Claims. (Cl. 209-17) This invention generally relates to thebeneficiating of minerals for use as direct products and/or furtherconcentration. More particularly, the invention relates to an improvedmethod and apparatus for beneficiating ores such as phosphate, iron,barite, feldspar, mica and potash in which the ores generally arebeneficiated for further concentration. The invention is not restrictedto ores alone, however, and in the case of minerals such as sand,limestone and coal, the beneiiciation may result in a direct endproduct.

Substantially all ores and other minerals are found in their nativestate admixed with impurities such as clays and other very finelydivided or colloidal particles. These impurities are harmful to themineral product itself, and in particular, hinder the processing ofores.

In the usual process of beneficiating ores or other minerals, the rawmineral material obtained from the natural mineral deposits is processedby washing, screening, etc., to remove trash therefrom and to separateand recover the larger mineral particles. In the case of ores, it iscommon to recover the raw mineral particles over 1%; inch by thispreliminary operation. These larger inch particles are usually suitablefor use without further processing. The remaining inch material,however, contains a mixture of the mineral particles and impurities offine material which must be further processed. The mixture of rawmaterial and liquid is generally referred to as a slurry.

When the raw mineral materials are mixed with Water or other liquid, thevery finely divided particles form slimes which interfere with furtherprocessing. The slime particles have a large surface and tend to absorbreagents, thereby making the cost of using a reagent prohibitive.Moreover, the slimes cause difliculty in the area of Selectivity of theend product. These slimes and other impurities therefore must be removedin order to make further processing economical. The removal of finematerial, including the slimes, is generally referred to as a deslimingoperation.

Many varied and different methods and apparatus heretofore have beenemployed to effect the desliming and/or other benefciation of ores andother minerals. Hydrocyclones and deslimers, in particular, are commonlyused for such beneficiation, The .prior art methods and apparatus,however, have not proven entirely satisfactory and have been beset withvarious disadvantages.

Most equipment of this nature is extremely bulky and difficult tohandle. A typical ore beneficiating unit, for example, may require asmuch as 5000 square feet of space. One of the major problems has been toreduce the size and space requirements for such units. Further, theprior art mineral beneficiating methods and apparatus have not been ableto recover sufficient amounts of the very small mineral particles. Theseparticles heretofore have been carried away with the slimes.

It is common to employ hydrocyclones in ore or other mineralbeneficiating units. A hydrocyclone is a generally cylindrical vesselcomprising a truly cylindrical section which merges into a generallyconical section. An opening is provided in the bottom or apex of thecone of the conical section, while another opening is provided in acover plate on the cylindrical section which is coaxial Hee with theapex opening. The opening in the cover plate generally has mountedtherein a pipe or tube of definite size extending down into thecylindrical chamber a predetermined distance. The pipe is known as avortex finder. In operation, a liquid suspension is supplied underpressure tangentially through a feed inlet to the cylindrical section ofthe hydrocyclone. The suspension is given a sufficient rotationalimpulse to keep it rotating during its passage through the hydrocyclone.As the swirling stream of liquid aproaches the apex of the hydrocyclone,a portion of it turns and begins to flow toward the opposite or base endof the machine. The heavier fraction of the solids is thrown toward thewall of the hydrocyclone and thereafter flows in a downward spiral tothe apex opening whereupon it is discharged. This discharge from theapex is known as the underflow of the hydrocyclone. The lighter fractionof the suspended solids is dragged or pulled into the uprising column inthe center of the hydrocyclone whereupon it is discharged through thevortex finder. This discharge from the vortex finder is known as thehydrocyclone overflow.

Due to the high velocity of the swirling liquid suspension in thehydrocyclone and the centrifugal forces created thereby, the surfaces ofthe hydrocyclone exposed to the moving suspension are subjected toexcessive abrasive wear and chemical breakdown, resulting in arelatively short useful life of the hydrocyclone. Attempts have beenmade to solve this problem by the use of sacrificial linings within thehousing of the hydrocyclone. These sacrificial linings usually arebonded to the housing of the hydrocyclone and are of a wear-resistantmaterial, such as rubber. Although these linings have increased theuseful life of the hydrocyclone, they nevertheless are also subject towear and consequently must be replaced in a relatively short period oftime. Moreover, the replacing of these linings necessitates a costlycurtailment of operations while the repair is being effected.

The operation of a hydrocyclone is readily affected by slight physicaland environmental changes such as changing the area of the feed inletentrance, changing the feed inlet pressure, and ychanging the insidedimensions of the hydrocyclone. A major problem in the use ofhydrocyclones has been how to make these changes readily andeconomically in one hydrocyclone without resort-ing to the use ofseveral different hydrocyclones. There has long been a need in the priorart for a single hydrocy-clone which can be readily changed to a varietyof sizes and/ or types as required.

Another apparatus commonly employed in an ore or mineral beneficiatingunit is a deslimer. In one type of conventional deslimer, raw feedmaterial which already may have been partially washed and deslimed orotherwise processed is introduced into one end of a long waterlledtrough or other container and a deslimed product is subsequentlydischarged through a bottom opening in the opposite end of thetrough.The desliming of the raw feed material is effected by upwardly flowingwater from the ybottom of the trough. As the raw feed material flowsalong the bottom of the trough in a generally horizontal directiontoward the discharge opening, the upwardly flowing water Washes thefines or slime particles from the larger particles of feed material. Theremoved slimes subsequently are carried upwardly and discharged into anoverflow launder disposed about the upper edges of the trou-gh While thedeslimed larger particles exit through the discharge opening in thebottom of the trough.

Although the 'above-described conventional deslimer provides areasonably leffective means of obtaining a deslimed product, it isnevertheless, subject to certain dis- J advantages. It is difficult toobtain the proper amount of control over the operation of such deslimerswhich is necessary to obtain the maximum degree off desliming.Consequently, an undesirable amount of slimes still remain entra-ined inthe deslimed product. More-over, such deslimers must be constructed of arelatively large size in order to obtain the capacity which is necessaryin the operation of an efllcient beneciating plant or unit. A majorproblem has been how to reduce the overall size of such deslimers andstill retain a capacity sufficient to handle the quantity of feedmaterial necessary for an eflicient beneilciat-ing operation.

Sumps are commonly employed at various stages in an ore or mineralbeneciating process to collect the slurry of raw feed material so thatit may be pumped to the next unit employed in the process. For example,when an ore beneilciating unit is initially started, a suflicient amountof slurry must rst be collected in a sump in order to create a pressurehead sufficient to operate a suction pump. Suction pumps often air lockand consequently, a certain pressure head is necessary to overcome theair lock to initiate operation -of the pump. The prior art has attemptedto solve this problem of creating sulllcient head by constructing highsumps. These sum-ps must be almost completely filled with a slurrybef-ore a sullicient head is created. Consequently, there is always thedanger of the sump running over. Also, the high sulmps add to thebulkiness of the beneciating unit.

To overcome the disadvantages o-f the prior art methods and apparatusfor beneflciating minerals, it is an object of the present invention toprovide `an improved method and apparatus for beneflciating mineralswhich is efllcient and economical and permits the recovery of a maximumamount of high grade mineral product.

Another object of the invention is to provide an improved apparatus forbeneciating ores which is relatively small and compact and yet which hasa capacity suflicien-t to meet modern industrial needs.

A further object of the invention is to provide an impr-oved method andapparatus `for de'sliming ores.

A still further object of the invention is to provide an improvedhydrocyclone which has an extremely wearresistant liner.

Another object of the invention is .to provide such a hydrocyclone whichhas a readily removable and replaceable liner.

Yet another object of the invention is to provide an improvedhydrocyclone which may be readily altered :to a variety of sizes and/ortypes as required.

A further object of the invention is to provide such a hydrocyclonehaving readily replaceable inserts to change the areas of the feed inletentrance and the apex discharge opening.

Another object of the invention is to provide an improved deslimer whichis of a relatively small size and yet has .a capacity sufficient tohandle the quantity of feed material necessary for an efficientbeneficiation operation.

Still another object of the invention is to provide such a deslimerwhich may be precisely controlled to obtain the maximum degree ofdeslim-ing.

Yet another object of lthe invention is to provide an improved meth-odyand apparatus for `desliming which utilizes a positive displacement ofthe liquid phase to effe-ct a positive desliming.

A further object of the invention is t-o provide an improved liquid.sump which is of a relatively small size and yet is capable ofproducing a pressure head sufficient to operate a suction pump.

A` still further object of the invention is to provide such -a sumpwhich eliminates the danger -of the liquid in the sump running overWhile the sufllcient pressure head is created to operate a suction pump.

A preferred embodiment of the apparatus of the present inventiongenerally comprises a feeder for supplying a feed of a ymineral slurryat constant volume and pressure, one or more hydrocyclones for effectinga preliminary particle -size separation .and partial desliming of theslurry, a deslimer for effecting a further desliming of the slurry, andscreening means to effect a size separation of the deslimed mineralparticles of slurry discharged Ifrom the deslimer. This apparatuspreferably is constructed in .the form of .a relatively compact unitwhich permits ease of handling.

In addition, the apparatus may include means for effecting a preliminaryprocessing of the slurry prior to its introduction into theabove-described unit. Such means may include a pri-mary sump forinitially receiving the mineral slurry, a primary pump, a feeder forreceiving the `slurry from the primary sump and maintaining it underconstant pressure, at least one or more first stage hydrocyclones foreffecting a preliminary sepa-ration of the slurry into a lighter linesphase and a denser mineral phase which results in -a higher recovery ofthe denser mineral phase, and a secondary sump for collecting the slurryso .that it subsequently may be delivered to the feeder of thepreviously described unit.

The hydrocyclone employed 'in the apparatus of the present inventiongenerally includes a body comprised of an outer housing and an innerceramic liner disposed within said housing, said liner being dividedinto a plurality of easily removable sections, said body defining acylindrical Ichamber at its base end which merges into a frus-t-oconical separating chamber at its opposite apex end, an inlet forintroducing a mineral slurry tangentially into the cylindrical chamberof said body, means for varying lthe size of said inlet, discharge meanscoaxial with said body for withdrawing ya lighter fines phase, and opendischarge me-ans disposed at the apex end of said body for withdrawing adenser mineral phase.

The deslimer of the apparatus of the present invention generallycomprises a tank lfor receiving said slurry, means for injecting a first.auxiliary liqud under pressure horizontally into said t-ank to move theparticles in said slurry horizontally therethrough, a porous bottom walln said tank to permit a second auxiliary liquid -to said bottom wallunder .a pressure suflicient to remove the smaller slime particles butnot the larger mineral particles -as said second liquid moves upwardlythrough said tank, means for overflowing and discharging the smallerslime particles from the upper end of said tank, and means fordischarging .the larger deslimed mineral particles from the bottom ofsaid tank.

The sump of the apparatus of the present invention generally comprises atank, an overflow reservoir to receive a liquid upon its initial entryinto said sump, said reservoir being situated above and adjacent theupper edge of one of the walls of said tank so that liquid overflowingfrom said reservoir passes into said tank, a discharge outlet in onewall of said tank, and means opposite said outlet for injecting anauxiliary liquid into said tank toward said outlet to increase Ythepressure head at said outlet.

In accordance with the method and apparatus of the present invention, amineral slurry is delivered to the primary sump from where it is fed toa feeder where it is maintained at a substantially constant pressurehead. From the feeder the slurry is injected tangentially into the firststage hydrocycloning zone under constant volume and pressure to effect apreliminary separation of t-he slurry into a lighter fines phase and adenser mineral phase resulting in high recovery of the denser mineralphase. The slurry comprised of the underflow of the denser mineral phaseis then fed to a secondary sump from Where it is delivered to a secondfeeder maintained at a substantially constant pressure head. The slurrythereupon is injected tangentially into the second stage hydrocycloningzone under constant volume and pressure to further separate the slurryinto a lighter lines phase and a denser mineral phase. The deliverypressure which the slurry has at the entrance to the second stagehydrocyclone is suflicient to cause the slurry to rotate around theportion of the hydrocyclone adjacent the entrance thereof and at leastpartially impinge upon itself without creating undue turbulence in theentire cylinder adjacent the entrance. This impingement causes ashearing action which scrubs and further deslimes the mineral particlesof the slurry. The denser mineral phase from the second hydrocyclone isthen delivered to a desliming zone whereupon a first auxiliary liquid isinjected under pressure horizontally into the desliming zone to move themineral phase horizontally therethrough. A second auxiliary liquid isintroduced upwardly into the desliming zone to remove the smaller slimeparticles but not the larger mineral particles. The slurry containingthe larger mineral particles is then discharged from the desliming zoneinto a screening zone whereupon the particles undergo a size separation.

The invention having been broadly described, it will now 'be describedin more detail with reference to the accompanying drawings in which:

FIGURE 1 is a schematic liow sheet illustrating the method and apparatusof the present invention;

FIGURE 2 is a front elevation view of an apparatus embodying variousfeatures of the present invention;

FIGURE 3 is a side elevation view of the apparatus shown in FIGURE 2;

FIGURE 4 is a cross sectional side elevation view of a hydrocyclone ofthe present invention;

FIGURE 5 is a cross sectional view along line A-A of FIGURE 4;

FIGURE 6 is a cross sectional side elevation view of a deslimer of thepresent invention; n

FIGURE 7 is a partial cross sectional View along line B-B of FIGURE 6;

FIGURE 8 is a top plan view showing the perforated bottom of thedeslimer of FIGURE 6;

FIGURE 9 is a sectional View of a portion of the bottom of the deslimershown in FIGURE 8;

FIGURE 10 is a side elevation view of a sump and pump of the presentinvention with the sump being shown in cross section;

FIGURE 11 is a cross sectional side elevation view .of the reservoirportion of the screen of the present invention; and

FIGURE 12 is a view along line C-C of FIGURE 11.

Referring to the drawings, the raw feed material, such as a mineralslurry, is delivered to a first or primary sump 11. The raw mineralmaterial prior to its delivery to the sump is processed by washing,screening, etc., to remove trash therefrom and to separate and recoverthe mineral particles over 3A; inc-h. These larger 3%; inch particlesare usually suitable for use without further processing. The remaininginch material, however, contains a mixture of mineral particles andimpurities which must `be further processed. The raw mineral material isgenerally mixed with a liquid to form a slurry for further processing.

The sump 11 includes an overfiow reservoir 12 to receive the slurry uponits initial entry into the sump, as best villustrated in FIGURE 10. Aside wall 13 of the reservoir is of a reduced size to provide anoverflow edge for the slurry in the reservoir to overflow into a tank14. The reservoir 12 is situated above and adjacent the upper edge ofthe back wall 15 of tank 14. Back wall 15 is inclined downwardly topermit the smooth flow of liquid from the reservoir to the bottom of thetank. Reservoir 12 and tank 14 are held in position by a frameworkgenerally indicated by the numeral 16.

upon its initial entry into the sump and thereafter discharge it oversidewall 13 in order to permit any air entrained in the liquid to escapetherefrom. This is important due to the fact that an excess amount ofair entrained in the slurry may cause an air lock in the suction pump19.

The reason for injecting an auxiliary liquid under pressure into thetank through pipe 18 is to create an artificial pressure head at outlet17. The increased pressure created lby the injection of the auxiliaryliquid permits the pump 19 to operate even though the liquid level inthe sump is relatively low. This important feature permits theconstruction of a relatively low sump since the injected liquid createsa sufficient head to operate the pump. Otherwise, it would be necessaryto construct a high sumpin order to build up a level of water in thesump sufficient to create a high enough pressure for the pump tooperate. Moreover, due to the artificial pressure head which is created,it is not necessary to fill the sump to a high level. rlhis has afurther advantage in that it eliminates the possibility of the sumprunning over.

The slurry is delivered from sump 11 to a feeder 22 by pump 19. Asubstantially constant pressure head is maintained in feeder 22 bykeeping the level of the liquid supply in the feeder relativelyconstant. The feeder 22 may have a lbypass leading back to the entranceinto the sump 11. When the system is initially put into operation, aconstant level of fiuid is quickly established in feeder 22 and theexcess then goes to the bypass 23 to be delivered 'back to the sump 11.After the system has been put into operation, the pump 19 can beregulated to maintain a constant volume in feeder 22 and the bypass 23no longer need be used.

From the feeder 22 the slurry is delivered under constant volume andpressure to a first stage hydrocycloning zone 24 to effect a preliminaryseparation of the slurry into a lighter fines phase and a denser mineralphase, resulting in a high recovery of the denser mineral phase. Apartial desliming also occurs in the first stage hydrocycloning zone 24.The first stage hydrocycloning zone includes at least one and preferablya plurality of hydrocyclones. The overflow comprised of the lighterfines phase of the slurry is discharged from the hydrocycloning zone 24to waste, or alternatively, water reclaimation, While the underow of thehydrocycloning zone comprised of the denser mineral phase is dischargedfrom the hydrocycloning zone and collected in a sump 51. Sump 51 issimilar in construction to sump 11 previously described. I

From the sump 51 the slurry comprised of the underow from the firststage hydrocycloning zone 24 is pumped to a feeder 52 by means ofsuction pump 53. A substantially constant pressure head is maintained infeeder 52 by keeping the level of the liquid or slurry'thereinrelatively constant. Feeder 52 is provided with a bypass 54 back to sump51 so that when the level of the liquid in the feeder 52 is sufficientto provide a constant pressure head, the excess may go to the bypass.The slurry is injected from feeder 52 tangentially into a secondhydrocycloning zone 55'under constant Volume and pressure for furtherseparation of the slurry into a lighter fines phase and a denser mineralphase. The second stage hydrocycloning zone includes at least one andpreferably a plurality of hydrocyclones.

A preferred type of hydrocyclone employed in the first and second stagehydrocycloning zones is comprised of a body 25 which includes an outerhousing 26 and an inner ceramic liner 27 disposed therein, as shown inFIGURE 4. The housing 26 may be constructed of any suitable materialincluding, metal, plastic and Fiberglas. The housing 26 may be dividedinto a plurality of removable sections. Each section of the housing isprovided with outwardly extending flanges 28 at its ends yfor connectionwith adjacent sections. The sections 7 are connected together by meansof nut and bolt assemblies 29.

The ceramic liner 27 is similarly comprised of a plurality of sectionswhich conform to the configuration of the outer housing 26. Liner 27 isnot bonded to housing 26 but fits loosely therein to permit easy removaland/ or replacement. The ceramic liner sections are slightly longer thanthe outer housing sections so that when the hydrocyclone is assembled,the sections of the ceramic liner are pulled together in a tight sealingrelationship. In addition, a sealing means, such as liquid neoprene, maybe disposed between the liner sections to effect a tighter seal. Sincethe ceramic liner floats freely within the housing, it may readilyexpand or contract Without braking.

The body 25 generally defines a cylindrical chamber 31 at its upper orbase end which merges into a frustro conical separating chamber 32 atits opposite apex end. Integrally connected with the body 25 in theregion of its cylindrical chamber end is a feed inlet 33 comprising apassageway 34 and an inlet port 35 opening into the cylindrical chamber31. The back side wall of passageway 34 is tangential with cylindricalchamber 31, while the opposite side wall of passageway 34 is tapered toan angle of at least and not exceeding 30 with respect to the tangentialback side wall. The front side wall of passageway 34 is preferablytapered to an angle of with respect to the tangential back side wall ofthe passageway. The inlet port 35 preferably is long and narrow topermit the entering slurry to be relatively evenly distributedvertically along a substantial portion of the walls of the cylindricalchamber. The outer end of feed inlet 33 is provided with outwardlyextending flanges 36 for connection to a delivery pipe 37. Means areprovided for varying the size of the inlet 33 comprising ceramic inserts45 which are adapted to lit into the bottom of the feed inlet.

The inlet 33 and the cylindrical chamber portion 31 of body are closedat their upper ends by a ceramic cover plate 38 which rests on the uppersurface of the ceramic liner section disposed within the cylindricalchamber and feed inlet of the hydrocyclone. In addition, cover plate 39constituting a portion of the housing, secures the ceramic liner coverplate 38 in place. Separating the ceramic plate 3S and housing coverplate 39 is a rubber gasket 40 which assists in sealing the upperportion of the hydrocyclone against leakage. A vortex nder pipe 42extends through the housing cover plate 39 and the ceramic liner coverplate 38 into the cylindrical chamber 31 of the body 25 to provide ameans for discharging the overflow comprised of the lighter tnes phaseof the slurry from the hydrocyclone. The vortex finder pipe 42 may bereadily adjusted to any desired predetermined distance into thecylindrical chamber. The vortex nder pipe 42 is coaxial with the body25.

An outlet 43 coaxial with the vortex finder 42 is provided at the apexend of body 25 for discharging the underflow comprised of the densermineral phase of the slurry from the hydrocyclone. Outlet 43 iscomprised of a removable ceramic insert 44 having an opening thereinwhich is secured to the apex portion of the hydrocyclone by acylindrical ange member 45.

It is to be noted that the ceramic liner 27 lines the entire innerportion of the hydrocyclone, including the inlet and apex dischargeopening, to provide a wearing surface for the slurry passing through thehydrocyclone. Moreover, the upper portion of the ceramic liner 27disposed within the cylindrical portion and the inlet of thehydrocyclone preferably is constructed as one integral piece. Theceramic liner is much more advantageous than the sacrificial wearresistant liners such as rubber, previously employed in that it has amuch longer life. This reduces the necessity of frequent costlycurtailment of operations while the liner is being replaced. Anotherimportant advantage of having removable liner sections resides in thefact that the sections may be varied to a number of different sizes toalter the physical dimensions inside the hydrocyclone to permitoperation under many different circumstances. It is also to be notedthat the ceramic insert 44 in the apex of the hydrocyclone permits thesize of the apex discharge outlet to be readily varied merely bychanging the size of the opening in the insert.

In operation of a hydrocyclone of the type just described, a rotatingbody of slurry is established and maintained in the confined space ofthe hydrocyclone. Additional slurry is then continuously deliveredtangentially under constant volume and pressure to the rotating body ofslurry in the region of the cylindrical end portion of the hydrocyclone.As the body of-slurry rotates in the hydrocyclone, a dual vorticalmovement is created whereby the outer portion of the rotating bodycontaining the denser mineral phase moves helically along and about theaxis of rotation toward the apex of the hydrocyclone while the innerportion of the rotating body containing the lighter nes phase moveshelically along and about an axis of rotation toward the cylindricalportion of the body. The slurry is delivered tangentially to therotating body through an entry zone or passageway having a boundary orwall which gives a directional vector of at least 10 and not exceeding30 with respect to the line of tangential entry to a portion of theslurry just prior to its tangential entry so that the denser mineralphase of the slurry is immediately thrown'to the outer periphery of therotating body. The denser mineral phase is then removed as underow atthe apex of the hydrocyclone while the lighter fines phase is removed asoverflow at the cylindrical base end of the hydrocyclone.

The operation of the tirst and second stage hydrocyclones may bedistinguished by the fact that the `first stage hydrocyclones areemployed to effect a high recovery of the mineral phase with a limitedamount of desliming while the second stage hydrocyclones are of the highimpingement type wherein a shearing action occurs which scrubs themineral particles of the slurry to effect a more complete desliming andseparation of the particles. By way of further explanation, in the rststage hydrocyclones, the slurry is injected tangentially so that itrotates around the cylindrical portion of the hydrocyclone and moveshelically downward into the frustro conical portion thereof Withoutimpinging upon itself. In the second stage hydrocyclones, however, theslurry is delivered tangentially to the cylindrical chamber of thehydrocyclone under a pressure sutlicient to cause the entering slurry torotate around the cylindrical chamber in a manner approaching laminarflow and at least partially impinge upon itself without creating undueturbulence in the entire cylindrical chamber. This impingement causes ashearing action among the particles of the slurry which scrubs thedenser mineral phase of the slurry. This shearing and scrubbing actionnot only further deslimes the slurry, but also prepares the densermineral phase of the slurry which is removed as the underflow from thehydrocyclone for a further desliming action. In eiect this preparationamounts to a partial loosening of the slime particles which still remainattached to the particles of the denser mineral phase so that the densermineral phase particles may be more easily deslimed in a subsequentdesliming operation.

Besides the difference in delivery pressure between the first stagehydrocyclones and the second stage hydrocyclones, the size of the inletof the second stage hydrocyclone is reduced by inserting the removableinserts into the bottom of the feed inlet. This reduction in size of theinlet of the second stage hydrocyclones combined with the increaseddelivery pressure causes the slurry entering tangentially into thesecond stage hydrocyclone to rotate completely around the cylindricalchamber of thelfhydrocyclone and at least partially impinge upon itseThe overflow of the second stage hydrocyclone 55 is delivered to adeslimer 60 for further desliming While the underflow thereof isdischarged to the sump 11 for reintrodu-etion into the system or,alternatively, discharged to waste.

The deslimer includes a generally V-shaped elongated tank 61 having afeed inlet 62 adjacent. the `top at one end thereof and a deslimedproduct discharge outlet 63 at the bottom of the opposite end of thetank. A plurality of spaced baffles 64 extend downwardly from the upperedge of thetank 61 and terminate at a point intermediate the top andbottom wall 65 thereof to form a channel 66 immediately .above thebottom for the passage of the particles of the slurry through the tankto the discharge outlet. The bottom wall 65 of the tank is porous orperforated to allow an auxiliary liquid to be introduced up wardly intothe tank through the bottom. Preferably, the bottom wall `65 iscomprised of a perforated plate 68 covered by a layer of perforatedneoprene material on its top and bottom sides thereof as shown in FIGURE9.

The auxiliary liquid is supplied under pressure to the bottom 65 bymeans of a liquid supply manifold 67 attached to the underside of thebottom wall. The manifold 67 is divided into a plurality of compartments70 by means of spaced partitions 71. Liquid is individually supplied toeach of the compartments 70 by means of conduits 72 connected to aliquid supply source. Valve means 73 are provided for individuallycontrolling the pressure of the liquid entering into each compartment70. Auxiliary liquid also may be injected under pressure horizontallyinto the tank 61 by means of an injector pipe 74 situated adjacent thebottom of the inlet end of the tank. The horizontally injected liquidmoves the particles of the slurry in the tank horizontally therethroughtoward the discharge outlet 63. The pressure of the horizontallyinjected auxiliary liquid may be controlled by valve means 75.

A slimes discharge launder 76 is disposed about the upper longitudinaledges of the tank 61 to collect the slimes which flow over the upperedges of the tank. The launder 76 is inclined downwardly toward thedischarge end of the tank.

Means are also provided for controlling the rate of discharge of thedeslimed particles through the discharge outlet 63 of the tankcomprising an elongated control rod 77 having a hollow rubber coveredstopper 78 at its bottom end an an adjusting wheel 79 at its upper end.The upper end of control rod 77 is threaded to permit the control meansto be screwed downwardly or upwardly to control the rate of discharge ofthe deslimed particles through the discharge outlet. The control rod isattached to the tank 61 by means of bracket -assemblies 81.

The discharge outlet 63 includes a Well portion 82 having a rubber linedpipe 83 connected at its bottom end thereof. The bottom end of the well82 and the pipe 83 are connected together by bolt assemblies 84 passingthrough flanges 85 on the bottom end of the well and a flange 86extending outwardly from the body of the pipe.

In operation of the deslimer, a mineral slurry is delivered to the feedinlet 62 of the deslimer from where it descends to the bottom of thetank 61. A first auxiliary liquid is injected under pressurehorizontally into the tank through pipe 7,4 to move the particles in theslurry horizontally through the tank. A second auxiliary liquidisintroduced upwardly into the tank through the porous bottom wall 65under a pressure sufllcient to remove the smaller slime particles butnot the larger mineral particles of the slurry upwardly through the tankto the discharge launder 76. The larger mineral particles continue theirgenerally horizontal movement through the tank to the discharge outlet.v

By adjusting the relative pressures of the-horizontally injectedauxiliary liquid and the upwardly flowing auxiliary liquid, it ispossible, to obtain very precise control over the removal of the smallslime particles from the 10 slurry passing through the tank. Forexample, if the pressure of the horizontally injected liquid wererelatively high in comparison with the pressure of the upwardly flowingliquid, substantially all of the particles in the slurry would .bedischarged from the tank with a minimum amount of desliming occurring.Similarly, if the pressure of the upwardly flowing liquid introducedinto the tank were relatively high in comparison to the pressure of thehorizontally injected liquid, substantially all of the particles wouldbe discharged into the overflow launder with a minimum amount ofrecovery of the larger deslimed particles from the bottom of the tank.

As shown by the arrows in FIGURE 6, when the pressures of the twoentering auxiliary liquids are properly adjusted for maximum deslimingefficiency, thev particles of the slurry passing through the tank aregiven an upward velocity vector as well as a horizontal vector so thatthey tend to move upwardly during their horizontal passage through thetank. The smaller slime particles are discharged into the overflowlaunder while the medium sized particles tend to strike the bailles inthe upper portion of the tank and be deflected downwardly into the flowof mineral particles being discharged from the bottom of the tank. Theheavier particles continue their generally horizontal path through thechannel formed in the bottom of the deslimer.

In the desliming operation just described, there is `amulti-displacement greater than one of the liquid phase of the slurrywhich effects a positive desliming under conditions approaching maximumefficiency. A major advantage inherent in the deslimer of the presentinvention resides in the fact that a relatively small unit can deslime aquantity of slurry sufficient to meet modern-day industrial needs. Forexample, a unit 3' x 8 x 4 high can effectively deslime up to 150 tonsper hour.

The overflow of slime particles from deslimer 60 is dis charged back tothe sump 51 for reintroduction into the second stage hydrocycloningzone, while the deslimed underflow of mineral particles 'from theydeslimer is passed through screening means 90 to effect a particle sizeseparation. It is to be noted, however, that it is not necessary tofurther screen the deslimed particles upon their disch-arge from thedeslimer. The screening operation` is required only if it is desired toseparate the particles into various sizes for further processing orbeneficiation. As shown on the schematic flow diagram of FIGURE 1 and inFIGURE 2, a plurality of screens may be employed in combination toeffect the desired particle size separation.

Referring now to FIGURE 11, each screening unit includes an inclinedscreening deck 91 of any `desired screen size and an overflow reservoir92 situated above and adjacent the upper edge of the screening deck. Abaille means comprising an angle iron 93 extends substantially acrossthe entire width of the reservoir 92 adjacent the back wall 94 at thebottom thereof. The lower end of baille 93 is spaced slightly from thebottom 95 of the reservoir to provide an outlet for an `auxiliary liquidsupplied to the back of the angle iron through supply conduit 96. Thepressure and volume of the auxiliary' liquid is controlled by valvemeans. The front wall 97 of reservoir-92 has an overflow lip 98 on itsupper end thereof and is of a reduced height to permit the liquid in thereservoir to overflow onto the screening deck 91. One or more freelyswinging plates 99 may be disposed immediately above the screening deck91 to assist in evenly distributing the liquid from the reservoir 92over substantially the entire width of the screening deck.I Arrangedbelow the screening deck 91 is a collection hopper 103 for collectingthe particles which pass through the screening deck.

In operation of the screening unit 90, the slurry containing theparticles to be separated is initially collected in the reservoir 90from where it overflows onto screening deck 91. An auxiliary liquid isintroduced into reservoir 92 behind the baffle 93 to repulp the slurryin the reservoir and assist in lifting the mineral particles in theslurry over the overow edge or lip 98. The mineral particles in theslurry have a tendency to be unevenly distributed in the reservoir 92when the slurry is collected therein. lf this situation is notcorrected, the particles will also be unevenly distributed when theslurry is overowed to the screening deck 91, thus interfering withmaximum screening eiciency. The introduction of the auxiliary repulpingliquid substantially alleviates this problem. The baffle 93 serves toevenly distribute the incoming auxiliary liquid substantially across theentire width of the reservoir, thus causing the mineral particles in theslurry to spread evenly across the entire width of the overflow edge asthe slurry is discharged from the reservoir.

In a typical screening installation employing a pair of screens incombination, the first screen would remove the -35 mesh particles. Thesecond screen would remove those particles between -16 mesh and -l-35mesh, with the oversize Igoing to storage.

In constructing a mineral beneficiating Iplant utilizing the method andapparatus just described, it has been found desirable to combine variouselements of the apparatus in a relatively compact unit which is easy totransport and handle. FIGURES 2 and 3 illustrate one such compact unit101. As shown in these figures, a feeder 51, one or more second stagehydrocyclones 55, a deslimer 60 and a plurality of screenin-g units 90are combined into a compact unit 101 supported by frame structure 104.An effective benefication of a mineral slurry can be obtained byemploying just the elements included in this structural unit, althoughfor the highest degree of beneficiation it is desirable to use theentire method and apparatus previously described. Using just thelast-named unit, however, a feed of mineral slurry is introduced intofeeder 51, from where it is supplied under constant pressure and volumeto one or more hydrocyclones 5S where a scrubbing and shearing of theparticles takes Iplace to effect a preliminary desliming and furtherprepare the particles for a subsequent desliming operation. The overflowof the hydrocyclone is discharged to waste, while the underflow issupplied to a deslimer 60. The overflow of slime particles from deslimer60 may be discharged back to the constant head feeder 51 forreintroduction into the system, while the underflow of deslimedparticles is passed through the screening units 90 to effect a particlesize separation.

A mineral beneficiating unit or plant constructed according to theprinciples of the present invention permits a substantial saving infabrication costs, replacement costs and operational and maintenancecosts. Moreover, such a plant may be constructed in a relatively smallspace as compared to most mineral beneficiating units presently used.For example, a typical prior mineral beneficiating plant requires asmuch as 5000 square feet of space, whereas a mineral beneficiating plantconstructed according to the principles of the present inventionrequires a space of as little as 50 to 75 square feet. In addition, thepresent invention permits the recovery of deslimed particles down to themicron size.

While the invention has been described with particular reference tospecific preferred embodiments, many other modifications may be made bypersons skilled in the art without departing from the scope of theinvention which is defined solely by the appended claims.

What is claimed is:

1. A method of beneficiating minerals which comprises:

delivering a slurry of a mineral to a hydrocycloning zone under constantvolume and pressure to separate said slurry into a lighter fines phaseand a denser mineral phase,

delivering said denser mineral phase to a desliming zone,

injecting a first auxiliary liquid under pressure horizontally into saiddesliming zone independently of said denser mineral phase to move saidmineral phase horizontally therethrough,

introducing a second auxiliary liquid upwardly into said desliming zoneunder a pressure sufficient to remove the smaller slime particles butnot the larger mineral particles,

and recovering the larger deslimed mineral particles from said deslimingzone.

2. A method as defined in claim 1 wherein said hydrocycloning zonecomprises two hydrocycloning stages in series, each of said stagesseparating feed slurry fed thereto into a lighter fines phase and adenser mineral phase, the slurry of said mineral delivered to saidhydrocycloning zone serving as feed slurry for said first stage, thedenser mineral phase from said rst stage serving as feed slurry for saidsecond stage and the denser mineral phase from said second stage servingas feed slurry for delivery to said desliming zone.

3. An apparatus for beneficiating minerals comprising:

feeder means for supplying a feed of a mineral slurry at constant volumeand pressure,

a hydrocyclone for effecting a preliminary particle size separation intoa lighter lines phase and a denser mineral phase of said mineral slurry,

means for delivering feed slurry from said feeder means to saidhydrocyclone,

a deslimer,

means for delivering the denser mineral phase of said slurry from saidhydrocyclone to said deslimer,

means separate from said denser mineral phase delivery means forinjecting a first auxiliary liquid under pressure horizontally into saiddeslimer to move the particles in said slurry horizontally therethrough,

means for supplying a second auxiliary liquid upwardly into saiddeslimer under a pressure sufficient to remove the smaller slimeparticles but not the larger mineral particles,

means for delivering the overflow of slime particles from said deslimerback to said feeder means for reintroduction into said hydrocyclone,

and means for discharging the larger deslimed mineral particles fromsaid deslimer.

4. An apparatus as defined in claim 3 which includes screening meanslfor effecting a size separation of said deslimed mineral particlesdischarged from said deslimer.

5. An apparatus as defined in claim 4 wherein said screening meanscomprises at least one inclined screening deck, a reservoir having anoverflow lip overhanging the upper edge of said screening deck, bafflemeans extending substantially across the entire width of said reservoiradjacent the bottom thereof and connected to the wall opposite saidoverflow lip, and means for introducing an auxiliary liquid through saidone wall behind said bafe means, said baille means serving to distributesaid auxiliary liquid evenly across the width of said reservoir tofacilitate lifting and effecting an evenly distributed overflow of thecontents of said reservoir onto said screening deck.

6. An apparatus Ifor positively desliming a mineral slurry comprising:

a tank,

inlet means for feeding a mineral slurry to said tank,

means separate from said inlet means for injecting a first auxiliaryliquid under pressure horizontally into said tank to move the particlesin said slurry horizontally therethrough,

a porous bottom wall in said tank to permit a second auxiliary liquid tobe introduced upwardly into said tank,

means for supplying said second auxiliary liquid to said bottom wallunder a pressure suicient to remove the smaller slime particles but notthe larger mineral particles as said second liquid moves upwardlythrough said tank,

means for overfiowing and discharging the smaller slime particles fromthe upper end of said tank,

and means for discharging the larger deslimed mineral particles from thebottom of said tank.

7. An apparatus for positively desliming a mineral slurry comprising:

a tank,

inlet means for feeding a mineral slurry to said tank,

means separate from said inlet means for injectin-g a first auxiliaryliquid under pressure horizontally into said tank to move the particlesin siad slurry horizontally therethrough,

a porous bottom wall in said tank to permit a second auxiliary liquid tobe introduced upwardly into said tank,

means for supplying said second auxiliary liquid to said bottom wallunder a pressure sufficient to remove the smaller slime particles butnot the larger mineral particles as said second liquid moves upwardlythrough said tank,

a plurality of spaced baffles extending downwardly in the upper portionof said tank and terminating at a point intermeidate the top and theporous bottom wall thereof to form a channel immediately above saidbottom wall for the passage of the larger mineral particles of saidslurry,

an overflow launder disposed about the upper edges of said tank todischarge the slime particles removed by said upwardly flowing secondliquid,

and an outlet in the bottom at one end of said tank for discharging saidlarger deslimed mineral particles.

8. An apparatus as defined in claim 7 which includes means forcontrolling the rate of discharge of said deslimed mineral particles.

9. A method for positively desliming a mineral slurry which comprises:

introducing said slurry into a tank,

injecting a first auxiliary liquid under pressure horizontally into saidtank independently orf said slurry to move the particles in said slurryhorizontally therethrough,

introducing a second auxiliary liquid upwardly into said tank under apressure sufficient to remove the smaller slime particles but not thelarger mineral particles of said slurry,

overflowing and discharging said slime particles from the upper end ofsaid tank, and

discharging the deslimed mineral particles from the bottom of said tank.

10. A method as defined in claim 9 wherein the volume of said first andsecond auxiliary liquids supplied to said tank is sufficient to effect amulti-displacement greater than one of the liquid phase of said slurryinitially introduced into said tank.

11. A screening unit for effecting a size separation of mineralparticles contained in a slurry comprising:

an incli-ned screening deck,

a reservoir having an overflow lip overhanging the upper edge of saidscreening deck,

a baille means extending substantially across the entire width of saidreservoir adjacent the bottom and connected to one wall thereof,

and means for introducing an auxiliary liquid behind said baffle meansthrough said wall, said baille means serving to distribute saidauxiliary liquid evenly across the width of said reservoir to facilitatelifting and effecting an evenly distributed overflow of the contents ofsaid reservoir onto said screening deck.

References Cited UNITED STATES PATENTS 439,961 11/1890 Lewis 209-2442,420,180 5/1947 Laughlin 209-454 2,735,547 2/1956 Vissac 209-2112,779,469 1/1957 Harris 209-211 3,068,802 12/1962 Costello 103-1133,071,249 1/1963 Rains 209-12 X 3,086,654 4/1963 Hollingsworth 209-12 X3,129,173 4/1964 Schulze 209-512 3,136,723 6/1964 Erwin 209-211 X3,207,310 9/ 1965 Yes-berger 209-211 X 3,261,559 7/1966 Yavorsky 209-158X 1,312,098 8/1919 Ceruti 209-173 3,008,574 11/1961 Clawson 209-123,008,575 11/1961 Clawson 209-12 FOREIGN PATENTS 559,092 6/ 1923 France.1,211,294 10/1959 France.

FRANK W. LUITER, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE 0F CGRRECTION Patent No.5,374,885 March 26, 1968 Floyd J. Clawson et al.,

It is certified that error' appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 4 line 39 for "n" read in Same-line 39 after "liquid to" insertbe introduced upwardly into said tank, means for supplying Said secondauxiliary liquid to Signed and sealed this 15th day of July 1969. n

(SEAL) Attest:

Edward M.F1etcher,1r. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

3. AN APPARATUS FOR BENDFICIATING MINERALS COMPRISING: FEEDER MEANS FORSUPPLYING A FEED OF A MINERAL SLURRY AT CONSTANT VOLUME AND PRESSURE, AHYDROCYCLONE FOR EFFECTING A PRELIMINARY PARTICLE SIZE SEPARATION INTO ALIGTER FINES PHASE AND A DENSER MINERAL PHASE OF SAID MINERAL SLURRY,MEANS FOR DELIVERING FEED SLURRY FROM SAID FEEDER MEANS TO SAIDHYDROCYCLONE, A DESLIMER, MEANS FOR DELIVERING THE DENSER MINERAL PHASEOF SAID SLURRY FROM SAID HYDROCYCLONE TO SAID DESLIMER, MEANS SEPARATEFROM SAID DENSER MINERAL PHASE DELIVERY MEANS FOR INJECTING A FIRSTAUXILIARY LIQUID UNDER PRESSURE HORIZONTALLY INTO SAID DESLIMER TO MOVETHE PARTICLES IN SAID SLURRY HORIZONTALLY THERETHROUGH, MEANS FORSUPPLYING A SECOND AUXILIARY LIQUID UPWARDLY INTO SAID DESLIMER UNDER APRESSURE SUFFICIENT TO REMOVE THE SMALLER SLIME PARTICLES BUT NOT THELARGER MINERAL PARTICLES, MEANS FOR DELIVERING THE OVERFLOW OF SLIMEPARTICLES FROM SAID DESLIMER BACK TO SAID FEEDER MEANS FORREINTRODUCTION INTO SAID HYDROCYCLONE, AND MEANS FOR DISCHARGING THELARGER DESLIMED MINERAL PARTICLES FROM SAID DESLIMER.